This application relates to ring blades or ring knives which are adapted for placement on a user's finger and which can be used for cutting.
Ring blades or ring knives are known and they have been used in the past to cut twine or thread or to cut plant stems. Some of the known ring knives have retractable blades so that the device can be carried relatively safely when it is not in use.
Early Canadian patent No. 219,333 issued Jun. 6, 1922 to O. L. Raymer describes a twine cutter comprising a ring and a cutter blade pivotally supported to project from the ring in a plane at right angles with the plane of the ring. There is a mechanism locking the blade in the open position When not in use, the blade can be folded into the ring so that the device can safely be carried in one's pocket. One difficulty with this known ring is that the ring device cannot be worn when the blade is moved to the retracted position. Thus, the blade is not available for immediate use and it is necessary to take the ring device and place it on one's finger after extending the blade to the open position. Accordingly, this known ring is not particularly suitable for use for defensive purposes.
Canadian patent No. 234,221 which issued Sep. 18, 1923 to P. P. Binkis describes a ring knife which also has a retractable blade. The blade is mounted in an elongate slit formed in the crown. The blade is fitted with an upper guide which can be moved by the user's finger in order to expose the sharpened edge of the blade. There is also a locking pin capable of locking the knife in either its operating position or in a retracted position. Because of the shape of the blade and its position relative to the crown of the ring, this known device is not believed to be particularly suitable as a defence ring.
Much more recent U.S. Pat. No. 3,648,371 which issued Mar. 14, 1972 to Charles Petrosky does describe a ring with a blade intended for defensive purposes. The ring is fitted with a downwardly pointed triangular blade with sharpened cutting edges and this blade is fixed in its position. This ring also has stabilizing wings which extend laterally from the ring. Because of the stabilizing wings and because the blade is fixed and exposed at all times, the ring is not particularly suitable for wearing at all times and under all circumstances. Because the blade is always exposed, there is a danger that it might inadvertently rip or tear an adjacent object or person causing undesirable damage or injury.
It is an object of the present invention to provide a relatively inexpensive ring blade which has a blade member which can be pivoted from a retracted position to an extended position where the sharp edge of the blade is exposed. The blade member is mounted in a slot in a movable crown and movement of the crown towards the adjacent top section of the ring will cause a pin mechanism to pivot the blade member to the extended position.
It is a further object of the present invention to provide a relatively simple ring blade with a pivotally mounted crown member having an elongate slot in which a blade member is mounted. The preferred ring blade can be worn at all times, even if the blade member is in the retracted position and the blade member can be pivoted to an extended position where its sharp edge is exposed by applying suitable pressure or force to the crown of the ring blade.